Thermal expansion of binary alkaline-earth borate glasses

The thermal expansivity of a number of calcium, strontium , and barium borate glasses are reported.The ex pansivity of the calcium and strontium borates increases with increasing alkaline-earth oxide concentration.Th e expansivity of the barium borate glasses is a m inimum at about 20 mole percent of barium oxide.The expansivity m easurem ents on the glasses were correlated with the d ensity m eas urements in the liquid range.The expan sivi ty of any composition is the lovvest in the glassy (solid) r egion and is greater in the liquid region.The expansivity in a third region which was d escribed as "very viscous" was not m easured but was indicated to be greater than in either of the measureable r egions.The density cur ves for each alkalin e-earth borate series converges with increasing te mperature.